1820.] Oxytnuriate of Lime. 407 



mately supplied by a quantity of oxygen gas exactly equal to it 

 in volume ; consequently we ought to have increased the produce 

 of oxygen gas by 20*33 cubic inches of oxygen gas. This indi- 

 cates an additional quantity of chlorine in the bleaching powder 

 equivalent to 40'66 cubic inches, or 31 grs. Now 31 grs. of 

 chlorine, in order to be converted into subbichloride of lime, 

 must unite with 50 grs. of Hme. We must, therefore, add 81 

 grains to the quantity of subbichloride of lime which we found 

 in the bleaching powder, and subtract 50 grains from the quan- 

 tity of uncombined hme, which we stated it to contain. This 

 wiU make the true constitution of the bleaching powder as 

 follows : 



Subbichloride of Hme 1408-9294 



Muriate of hme 41 9-6890 



Water 755-9800 



Loss 129-4016 



2714-0000 



The true composition then of the bleaching powder reduced 

 to 100 parts is as follows : 



Subbichloride of lime 51-91 



Muriate of hme 15 46 



Water 27-86 



Uncombined lime , 4-77 



100-00 



So that rather more than half of the powder consisted of pure 

 subbichloride of hme, while the remainder consisted of matter of 

 no eflGicacy for bleaching. 



I was long at a loss to account for the great proportion of 

 water which this specimen of bleaching powder contained ; but 

 I now conceive that the following explanation will enable us to 

 account for it. The sulphuric acid used in the process was vei-y 

 weak; namely, about the specific gravity 1-5, instead of 1-75, 

 which is the specific gravity required by law in Great Britain. 

 The consequence would be that a portion of the water of the 

 acid would be driven over into the receiver along with the chlo- 

 rine gas by the heat required to disengage that gas. 



The extraordinary strength of the specimen, which will sur- 

 prise both manufacturers and bleachers, and which, I have reason 

 to believe, greatly exceeds what can possibly be made in the 

 large way by the usual process, is most probably owing to its 

 having been taken from the surface of the lime exposed on the 

 bottom of the receiver, which is always much nearer a state of 

 saturation than any other portion of the powder. The specimen 

 examined, therefore, serves rather to show to what strength the 

 bleaching powder can bo made than to give a fair sample of 



6 



